Subaru Forester blowing globes

Submitted: Tuesday, Jun 09, 2020 at 20:37
ThreadID: 140129 Views:8449 Replies:8 FollowUps:11
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Hi, My 10+ y.o Forester keeps blowing headlight globes. Keep replacing them, used several brands, careful not to touch the globe with bare fingers when handling, but they all go. Parkers, hi, lo, they last about 4-6 months only
My thinking is that there should be a cause other than the quality of the replacement globes. Any ideas from the forum?
Cheers
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Reply By: Athol W1 - Tuesday, Jun 09, 2020 at 21:54

Tuesday, Jun 09, 2020 at 21:54
Have you checked the voltage that is being applied to the lights.

Light globes can be quite sensitive to voltage, generally more so if voltage too high but can also apply to excessively low voltage.

Headlight ideal voltage is around 13.2 to 14 when measured at the globe with the engine running at about 1500rpm. Too high will be an Alternator fault, to low either alternator (check at rear of alternator) or undersize wiring (most likely). Measure the voltage ACROSS THE GLOBE, And also to earth.

Regards
Athol
AnswerID: 632056

Reply By: RMD - Tuesday, Jun 09, 2020 at 22:16

Tuesday, Jun 09, 2020 at 22:16
CSeaJay
In my opinion, the only cause can be, far too high alternator regulated voltage, either constantly or intermittent. Never seen any earlier LC Toyotas blow globes with the 11 volts or so they apply to the headlights but plenty of globes blow with elevated voltages. Are the normal globes which have blown shiney on the inside glass? Not apparent with halogens headlight globes usually. Testing the alternator voltage would be the first thing to do. As mentioned above the voltage should be around that. Some replacement globes are rubbish and will not last anyway, maybe that is also a problem.
A ten year old Forester should have good quality globes from new, like Toyotas and Mazda have in the past, Those original globes lasted longer than many popular cars. This sounds like a stupid idea but is what I and a wrecker mate used to do, Use/source used globes from crashed cars of known quality brands and you don't have to replace globes for years to come, IF the voltage is correct. Hard to buy quality in todays world. How do you know what is what.
Also,
Your vehicle may have an intermittent connection of some wiring, ie, dirty loom plug or loose earth strap, which sometimes leaves the alternator, momentarily disconnected from battery and allowing the alternator reg to be, "unsensing" of battery voltage in that moment, and the resulting voltage spike WILL blow globes easily.

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Reply By: qldcamper - Wednesday, Jun 10, 2020 at 09:09

Wednesday, Jun 10, 2020 at 09:09
What kind of driving do you do? Lights constantly turned on as many people do these days on rough roads will test any bulb/globe.
Do your rear lights fail too?
AnswerID: 632059

Follow Up By: RMD - Wednesday, Jun 10, 2020 at 10:19

Wednesday, Jun 10, 2020 at 10:19
A good point regarding rough roads and light use. If the vehicle has done some KM's and the front shocks are stuffed, the resulting repetitive road shocks transmitted to the body on rougher roads will blow the filaments out of the globes, probably even when turned off too. No shock dampening destroys many things.
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Reply By: HKB Electronics - Wednesday, Jun 10, 2020 at 09:23

Wednesday, Jun 10, 2020 at 09:23
Does the charge light come on before you turn the motor over, if not it is probably blown, without it working you will not get an indication if the alternator is faulty.

Check charge voltage as suggest, if lights flare when you rev the motor voltage regulator is most likely faulty or there is a problem with the voltage sensing circuit.

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Reply By: CSeaJay - Wednesday, Jun 10, 2020 at 12:39

Wednesday, Jun 10, 2020 at 12:39
Thank you all, helpful comments.
It is a city car, no fault lights come on, and seem to be only the front lights.
Based on comments above I will check the alternator and the voltage at the lights
Thanks again
AnswerID: 632066

Reply By: Allan B (Sunshine Coast) - Wednesday, Jun 10, 2020 at 12:57

Wednesday, Jun 10, 2020 at 12:57
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Hi CSeaJay,
There are really only two reasons for premature failure of lamps..... excessive mechanical vibration or excessive voltage.
I doubt that a Forester is "excessively vibrating" so it is likely to be over-voltage. Auto lamps are usually rated at 12-16 volts but will last longer when run at 12v rather than 16v.
If you can, apply a voltmeter to the headlamps and compare the voltage at idle and then at increased revs.

One reason for system over-voltage is a battery in poor condition where it has developed high internal resistance. Another very likely cause of excessive voltage being applied to your lamps is poor battery connection. If any of the battery connections, both positive or negative are less than 100% then the alternator will hold the car's wiring loom well above the nominal 12 volts and this high voltage will be applied to your lamps.
If this were the problem you will notice the headlamp brightness increasing as the engine is raised above idle speed. It would also show up as reduced starter performance.
If you suspect connection issues then remove and clean connections at both ends of the battery earth strap, both positive and negative battery posts, and all cable terminations to the positive battery connections.
Poor connections in the headlight wiring or at the lamps may cause lowered light levels but will not cause lamp failure.

One other possibility..... have you offended another driver wearing a black pointy hat? lol



Cheers
Allan

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Follow Up By: RMD - Wednesday, Jun 10, 2020 at 14:48

Wednesday, Jun 10, 2020 at 14:48
G'Day Allan,
I mentioned the vibes above because my 2011 Dmax when NEW, had new shocks which allowed 7 oscillations of the torsion bar front end over every bump. It fairly flapped around, and I could feel it too. I recorded the sound and placed the sound file in an audio analysis program. On screen you could clearly see 7 peaks, which reduced to 1.3 peaks after fitting shocks which worked. OE ones totally unable to control frontend despite being new. I still have those shocks in the shed and they look brand new, just rubbish. If CSeayJay's Forester is shock deficient it will certainly cause unusual vibes up front I reckon similar to what QLD Camper mentioned. Shouldn't happen, but may be going unnoticed and may be part of the cause.
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Follow Up By: Allan B (Sunshine Coast) - Wednesday, Jun 10, 2020 at 16:32

Wednesday, Jun 10, 2020 at 16:32
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Hi RMD,
You may well be right, although I know a couple with Foresters who would be very quick to involve me if they were having any electrical problems. Which is why I said "I doubt it". And after all, it was a Dmax!!

CSeaJay..... Was there a time when you had no problem with the lights? Is it a more recent behaviour? And bearing in mind what RMD has said, is your Subie's front end 'less than perfect'?
Cheers
Allan

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Follow Up By: Frank P (NSW) - Wednesday, Jun 10, 2020 at 20:46

Wednesday, Jun 10, 2020 at 20:46
I've got to ask a question here.

Shock absorbers do not absorb shock.The springs do. The " shock absorbers" are dampers to control the springs - perhaps control compression and certainly to control rebound.

If "shock absorbers" are set to control compression, ie increase resistance to compression, wouldn't they increase "shock" to the rest of the body and therefore shake the ^&it out of lamp filaments?

And if they control the rebound, which they should do, well, I cannot see how this can adversely transmit to the vehicle body because in the rebound there is nothing being "punched up" to the body.

This is not a rhetorical question. I would like someone to explain it to me.

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FrankP

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Follow Up By: Allan B (Sunshine Coast) - Wednesday, Jun 10, 2020 at 21:50

Wednesday, Jun 10, 2020 at 21:50
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Frank, you have opened Pandora's Box. This could be "interesting" to say the least.

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Allan

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Follow Up By: CSeaJay - Wednesday, Jun 10, 2020 at 22:07

Wednesday, Jun 10, 2020 at 22:07
Allan, Frank, RMD
No problem with the front end, and had a decent suspension service as well.
Problem existed the last two years or so. I will definitely check the voltage at the lights as you and others suggested, and also clean the battery terminals in any case.
Thank you for the good advice
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Reply By: Member - cruza25 - Wednesday, Jun 10, 2020 at 16:03

Wednesday, Jun 10, 2020 at 16:03
It’s a Subaru thing

Great cars and fantastic reliability

My 2008 forester and I have 3 friends with 08-11 all suffer with failing globes. The dealerships offered no help or advise but were happy to replace them for a fee.

Just buy a dozen decent brand ones on eBay, you get quite proficient after a few goes especially on the drivers side because you have to remove the air duct.
Cheers
Mike

Ps. Just replaced the subie with a Honda ( wife’s decision)
AnswerID: 632072

Follow Up By: Zippo - Wednesday, Jun 10, 2020 at 18:55

Wednesday, Jun 10, 2020 at 18:55
I think I've replaced two in 90,000 on my 07 Foz. SWMBO's Corolla has done 56,000 and I've done one - hers is all city driving, mine is all the outback trips. Go figure, not a lot of difference and I get all the corros.

To the OP: yes check the alternator voltage AND battery voltage, looking for a difference. There are a zillion earths hanging out of all the harnesses, and one loose one can cause some very hard to deal with faults. Basically need to check more than just the voltages ...
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Follow Up By: RMD - Wednesday, Jun 10, 2020 at 22:42

Wednesday, Jun 10, 2020 at 22:42
cruza25
Adding bandaide globes to a fault isn't fixing it though. Seems to be, if others have the same problem too there is a wiring size deficiency in those vehicles.

Similar example. Just replacing fuses doesn't fix a fault either!
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Reply By: Member - David P (WA) - Wednesday, Jun 10, 2020 at 19:38

Wednesday, Jun 10, 2020 at 19:38
Hi CSeaJay

I have a 2010 Forester and the problem will be as others have said high voltage. On my car when you turn the lights on the alternator voltage goes to over 14 volts. Good if you want to charge the battery quickly but a killer for 12 volt globes. I tried various headlamps and have had the most success with 'long life' globes which I think are from Phillips.

Cheers
David
AnswerID: 632080

Follow Up By: RMD - Wednesday, Jun 10, 2020 at 20:28

Wednesday, Jun 10, 2020 at 20:28
David. Good info and observation. If so, the turning on the lights must be bleeding the alternator sensing voltage to it't regulator sense wire, therfore causing higher voltage to occur. A simple small relay which closes and connects battery voltage to the sense wire wouls solve the problem and allow the regulator to then directly sense what the battery voltage really is. Possibly dirty connection in loom plug or connection or the wiring is thin OR overloaded by an accessory being added quite innocently.
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Follow Up By: HKB Electronics - Wednesday, Jun 10, 2020 at 21:29

Wednesday, Jun 10, 2020 at 21:29
The sense wire is connected via a fuse to the busbar in the main fuse box, assuming no one altered the circuit the headlights shouldn't affect the alternators output voltage. But as it has permanent 12V on it someone may have tapped into that circuit as you hint for driving lights etc.

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Follow Up By: RMD - Wednesday, Jun 10, 2020 at 22:38

Wednesday, Jun 10, 2020 at 22:38
HKB
Sort of reverse to what is done with an earlier Toyota LC by adding a diode in the sense line to make it higher. In this case it seems starved of correct battery voltage. Assuming the reg is healthy.
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